Battery PX14, 2.6v, 2.7v, 2.8V, 3v.....

[Alcayatas]

Hello,

long time ago I was bought a super8 camera Carena 756, and photometer battery ask for a PX14 battery of 2.6V. I couldn't find this battery, and I used two button 1.5v battery, so as a result I have a 3V battery. But unfortunatelly the film was overexposed due to this, so this slightly differences was afectation on the film exposure.
Some time later, I bought another super8 camera, and inside there was and old battery PX14, but to 2.7V. So was a different voltage, for the same battery number? Even today we can find some bateries at 3V. I know this kind of batteries are used also in other photo, and cinema cameras, or photometers.
Some shops also sell a equivalent , or two A675 1.4V battery, so you get 2.8V. also named as a PX14 replace battery. Other sell a 3V battery for equivalent.

So I always have some questions about it.

-What they do this differents types of voltage batteries and give it the same name PX14? 2.6v, 2.7v,
-What they decided do a very different voltage battery, as usuals, like 1.5V, 3V,... It is not easy manufacture the cameras to standards voltages?

Thanks

 

[Nitroplait]

The old batteries were mercury based and abandoned/prohibited due to environmental reasons. These batteries were widely used because they were long lasting and had a good depletion profile. Cameras were made to expect the voltage of these batteries, typically 1.3-1.4V and multiples: 2.7V-2.8V, 5.4V-5.6V

The current closest available substitute is zinc-air (hearing aid batteries) which will provide a voltage and depletion profile similar to the mercury - but zinc-air will last much shorter.
They will often need to be adapted as they are not meant to be used in cameras, but in hearing aid devices.
Wein makes some overpriced substitute batteries if you don't want to adapt common Zinc-Air yourself.
There are dumb zinc-air adapters available on eBay and elsewhere.

Modern cameras are typically made to use alkaline (1.5V), silver oxide (1.55V) or lithium - if you use these batteries in old cameras calibrated for mercury batteries, you will often need a voltage converter to avoid a too optimistic meter reading.
Sometimes you can just compensate by adjusting the ASA/DIN setting - but the resulting readings may not be linear throughout the scale.
Voltage converter adapters will often cost more than the dump adapters.

Examples of battery converters: https://www.kantocamera.com/english/adapter/adapter_en.html

 

[beemermark]

More likely reason was the camera meter failing.

 

[Dan Fromm]

I've used Gossen's PX14 adapter https://gossen-photo.de/en/produkt/battery-adapter-set/ with good results in my Canon 814AZ. See https://www.smallbattery.company.org.uk/sbc_px14_adapter.htm, who sell the same adapter, for dimensions.

https://polarbearcamera.com/products/px14-adapter seems to do much the same but doesn't seem to reduce/regulate voltage, so must be used with the appropriate hearing aid batteries.